Vukmir, a state senator from Brookfield, has already lined up some 500 endorsements from party leaders and the grass roots, a testament to her long career in elective office and before that, as a political activist.

By contrast, Nicholson is running for public office for the first time. He has spent months trying to gain support from many of the same people who have known Vukmir for years.

Along the way, Vukmir has picked up some intriguing support.

Joel Kleefisch, a state legislator and husband of Lt. Gov. Rebecca Kleefisch, is backing Vukmir.

And on Tuesday, Rachel Campos-Duffy, the wife of U.S. Rep. Sean Duffy, joined Tonette Walker as co-host of a fundraiser for Vukmir.

The lieutenant governor and congressman are neutral in the race.

Why does all this matter?

The Vukmir and Nicholson campaigns are trying to secure an official endorsement from the Republican Party when delegates meet in May in Milwaukee.

A candidate has to get 60% support from the delegates to claim the party backing heading into the Aug. 14 primary. Vukmir and Nicholson are bidding to take on Democratic U.S. Sen. Tammy Baldwin in November.

Delegates will have to figure out for themselves the meaning of the moves by the political spouses.

"I think people recognize that each individual spouse in a marriage is entitled to their own opinion," said Dave Anderson, who has attended every GOP state convention since 1978 and worked for Republican governors Walker, Tommy Thompson and Scott McCallum.

"But I think it is significant when a spouse of an elected official makes a commitment," added Anderson, who said he was leaning toward Vukmir in the race but hasn't officially endorsed. "I think it has meaning and people read a lot into that."

Tonette Walker gave a strong endorsement of Vukmir in a Wisconsin State Journal opinion piece. She wrote: "When a Republican woman stands for our Wisconsin principles, votes the right way and is ready to shake things up for America, it is our duty to support her."

Anderson isn't surprised at the support Vukmir has picked up — she has won a series of straw polls on local party caucus events. After all, she has been an elected official since 2002, winning the Assembly seat Walker held before becoming Milwaukee County executive.

"I think the greatest strength she has is she's a known quantity," Anderson said. "The greatest challenge Nicholson has is he needs to establish himself and needs to get to know people over a period of time like Leah has."

Vukmir's campaign certainly isn't shy about allying the state senator with Walker's agenda.

"It's no surprise that in-state conservatives who understand what's truly important to the grass roots are backing Leah," said Vukmir campaign manager Jess Ward.

Vukmir received some small financial backing last year from two GOP county parties, according to state records, $500 from Barron County and $200 from Price County. Carol Cady, chairwoman of the Vilas County GOP, endorsed Vukmir, as did Bob Spindell, 4th Congressional District GOP chairman.

There have been numerous Republican events attended by Walker, Nicholson and Vukmir, including Lincoln Day dinners in Kenosha, Eau Claire and Manitowoc and the 1st and 7th congressional district caucuses.

Several prominent Walker backers support Nicholson, including Lake Forest, Ill., businessman Richard Uihlein and Mary Stitt, who is leading Nicholson's in-state fundraising effort.

The Nicholson campaign also points to 8,000 Wisconsinites who have made financial contributions to the effort. In a head-to-head matchup among likely Republican primary voters, the Marquette University Law School Poll showed in early March that Nicholson had 28% support and Vukmir 19%. Forty-nine percent said they don't know who they'll vote for.

Jim Klauser, a longtime GOP insider who was a top aide to former Gov. Tommy Thompson, is the honorary co-chair of Nicholson's campaign.

He remains confident that Nicholson will gain the GOP nomination and beat Baldwin in the fall.

"I support Kevin Nicholson because he is the only candidate who can — and will — beat Tammy Baldwin," Klauser said in a statement. "I’ve seen a lot of campaigns; Kevin has the story, depth of understanding, and the team that Republicans need to win in November. That’s why he’s winning this primary. I support the governor as well, and am taking him at his word that he’ll remain neutral in this race."